We would occasionally (pre 8.8) see scheduled tasks immediately fail on every single device, right after hitting Start Now. Resetting the package hash would always immediately fix the problem. This would happen to packages that have been deployed before, and packages that were brand new, it made no distinction.

Now, we upgraded to 8.8 and installed SP1, and in the documentation for SP1 it said that it fixed an issue where scheduled tasks would spontaneously and immediately fail (I'm talking immediate -- even before discovering agents or caching files or anything.

We have strange goings on with tasks since SP1, Some Tasks sit in active for hours and I found that its taking 1 minute per file to hash - doesnt seem to happen every time and is intermitent. They do start eventually (sometimes), but is very anoying as we are not sure if they are going to work or not.

Since nobody seems to have an obvious fix then I would suggest you get yourself up to service pack 2 which is the current service pack. If the issue still exists then you can get this logged with LANDesk and properly supported because you will be at the latest SP level.